FIG. 1 shows the structural diagram of a front side of a tray of a conventional optical disc drive, and FIG. 2 shows a structural diagram of a back side of the tray of the FIG. 1. After the conventional tray 10 is made, e.g. the conventional tray 10 made by using an extrusion, the tray 10 has to be measured precisely to make sure the size of each component arranged on the tray 10 and the relative sizes between the components. These sizes must meet a product specification such that they can be really arranged in the optical disc drive. After a measurer finishes measuring each component on the front side of the tray 10, he will continue to measure each component on the back side of the tray 10. Since the front side and the back side of the tray 10 do not have a common measuring standard, when measuring the back side of the tray 10, the tray 10 has to be turned to the back side from the front side. However, as soon as the tray 10 moves, the measuring standard will have deviation, and the tray 10 cannot precisely keep the measuring standard used by the front side and that used by the back side. Therefore, it is hard to measure the tray 10 more precisely.
In view of the shortcomings of the above mentioned prior art, the inventor of the present invention wants to improve and invents a tray with a measuring dimensional accuracy mechanism.